Join the two users controllers but split out role setting

test/controllers/users/roles_controller_test.rb

@@ -0,0 +1,22 @@
+require "test_helper"
+
+class Users::RolesControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    sign_in_as :kevin
+  end
+
+  test "update" do
+    assert_not users(:david).admin?
+
+    put user_role_url(users(:david)), params: { user: { role: "admin" } }
+
+    assert_redirected_to users_path
+    assert users(:david).reload.admin?
+  end
+
+  test "can't promote to special roles" do
+    assert_no_changes -> { users(:david).reload.role } do
+      put user_role_url(users(:david)), params: { user: { role: "system" } }
+    end
+  end
+end